Chiari Malformation

Chiari malformation is a condition that affects the connection between the brain and spinal cord, specifically at the base of the skull. It occurs when part of the brain tissue, called the cerebellar tonsils, extends downward through the opening at the base of the skull (the foramen magnum) into the upper spinal canal. This can put pressure on the spinal cord and block the normal flow of cerebrospinal fluid (CSF), leading to a range of symptoms. 

At Banner Health neurosciences, our neurologists and neurosurgeons specialize in diagnosing and treating Chiari malformation using advanced imaging and surgical techniques to relieve pressure and protect long-term brain and spinal function. 

How common is Chiari malformation? 

Chiari malformation occurs in about 1 in every 1,000 births in the United States. Many cases are discovered incidentally during imaging for other reasons, while others are diagnosed after symptoms begin. 

Is Chiari malformation hereditary? 

There is growing evidence that Chiari malformation may have a hereditary component, meaning it can sometimes run in families. However, research into its genetic causes is ongoing. 

What causes Chiari malformation? 

Chiari malformation most often develops because the base of the skull is smaller or misshapen, which causes part of the cerebellum to be pushed downward into the spinal canal. This creates crowding near the brain and spinal cord, disrupting the flow of cerebrospinal fluid and increasing pressure on the spinal cord. 

In other cases, Chiari malformation can develop later in life due to injury, infection or excessive loss of spinal fluid. 

When are you at risk for Chiari malformation? 

Chiari malformation is more common in women than men. Type II Chiari is also more frequently seen in people of Celtic descent. 

Certain health conditions can increase the risk of developing or worsening Chiari malformation, including: 

• Hydrocephalus (buildup of fluid in the brain) 
• Tethered cord syndrome 
• Myelomeningocele, a form of spina bifida 
• Syringomyelia, when a syrinx (a fluid-filled cavity) forms within the spinal cord 

Types and symptoms of Chiari malformation 

Type I (most common) 

In Chiari type I, the cerebellar tonsils extend slightly below the base of the skull. This type is often not discovered until late childhood or adulthood. 

Common symptoms of Chiari type I include: 

• Headaches that worsen after coughing, sneezing or straining 
• Neck pain and stiffness 
• Dizziness or balance problems 
• Numbness or tingling in the hands or feet 
• Difficulty swallowing, sometimes with gagging or vomiting 
• Poor hand coordination 

Less common symptoms may include: 

• Scoliosis related to spinal cord tension 
• Sleep apnea or abnormal breathing patterns 
• Tinnitus (ringing or buzzing in the ears) 
• Irregular heart rhythm 

Type II 

Chiari type II involves a greater degree of brain tissue extending through the opening at the base of the skull. It is often diagnosed in infants, usually along with myelomeningocele (a type of spina bifida). 

Symptoms of type II Chiari can include: 

• Swallowing difficulties 
• Weakness in the arms 
• Changes in breathing 
• Rapid, downward eye movements 

Type III 

Chiari type III is the rarest and most severe form. In this type, parts of the cerebellum or brainstem extend through an abnormal opening in the back of the skull. It is typically detected on ultrasound during pregnancy or at birth. 

This type can cause serious neurological complications and has a higher risk of mortality compared to types I and II. 

How is Chiari malformation diagnosed? 

Diagnosis begins with a physical and neurological exam, followed by magnetic resonance imaging (MRI)—the most effective tool for identifying Chiari malformation. 

MRI provides clear, detailed images of the brain and spinal cord, helping your doctor see if the cerebellar tonsils are extending into the spinal canal or if a syrinx (a fluid-filled cavity) has formed in the spinal cord. 

Other diagnostic tests may include: 

• CT scans to evaluate bone structure at the base of the skull 
• Neurological testing to assess balance, strength and reflexes 
• Cine MRI, which measures the flow of cerebrospinal fluid around the brain and spinal cord 

Treatment for Chiari malformation 

Treatment depends on the type and severity of your symptoms. 

• Monitoring: If you have mild or no symptoms, your doctor may recommend regular neurological exams and periodic MRIs. 
• Medication: Pain management and anti-inflammatory medications may relieve headaches or neck pain. 
• Surgery: For patients with significant symptoms or evidence of spinal cord compression, the most common procedure is posterior fossa decompression surgery. 

During this surgery, the neurosurgeon removes a small section of bone at the back of the skull and upper cervical spine to relieve pressure on the spinal cord and improve cerebrospinal fluid flow. In some cases, the dura mater (the protective covering of the brain and spinal cord) is opened and patched with tissue or synthetic material to create more space for the part of the brain that has shifted downward. 

Recovery varies by individual but typically involves close monitoring, imaging follow-ups and physical therapy. 

Living with Chiari malformation 

With appropriate treatment, many people with Chiari malformation experience significant relief of symptoms and can return to normal activities. Ongoing care with your neurologist or neurosurgeon helps monitor changes and maintain quality of life. 

At Banner Health, our experienced team offers advanced diagnostic imaging, surgical expertise and compassionate support for you and your family every step of the way.